Asthma is one of the most common chronic illnesses and it disproportionately affects disadvantaged populations residing in urban areas. Mouse allergen exposure, in particular, appears to play a critical role in the urban asthma epidemic for several reasons: (1) Mus m 1, the major mouse allergen, is found in 95% of inner-city homes, and is found in 100-fold higher concentrations in inner-city homes than in suburban homes; (2) As many as 25-50% of children with asthma living in urban areas have evidence of IgE-sensitization to mouse, making them susceptible to mouse allergen-triggered asthma symptoms; and (3) Home mouse allergen exposure is associated with more symptoms days, more rescue medication use, and more asthma related health care use among IgE-sensitized children with asthma. Although these are compelling observations, demonstrating that a reduction of mouse allergen exposure results in Improved asthma health in mouse-sensitized children with asthma is critical for establishing a causal role for mouse allergen exposure. Preliminary evidence indicating that a mouse allergen-targeted environmental intervention (MA-EI) is efficacious in reducing settled dust Mus m 1 levels by >75% provides the final piece of background data to support the hypothesis that a MA-EI will reduce asthma morbidity in mouse-sensitized individuals with asthma. To test this hypothesis, we propose conducting a multi-center, randomized clinical trial of MA-EI at two major Northeastern US urban centers with high prevalence of asthma and mouse sensitization and high home Mus m 1 levels. Aim 1 is: To determine the efficacy of this MA-IE to: (a) Reduce asthma symptoms and rescue medication use, (b) Reduce asthma-related health care utilization, and (c) Improve physiologic and inflammatory markers of asthma disease activity among mouse-sensitized children with asthma. Aim 2 is: To evaluate mouse-specific IgG and IgE as biomarkers of allergen exposure and asthma clinical status. The findings from the clinical trial will lend critical insight into the impact of home mouse allergen exposure on urban populations with asthma, and directly inform public health strategies to reduce the inner-city asthma burden.